Method and a device for determining the temperature at viscosity measurements

ABSTRACT

Two capillary-viscometers which are identical except for differing as regards the extent to which the width of their capillaries depends on the temperature, are simultaneously used for identical measurements under identical conditions. The ratio of the two measuring values is a direct indication for the exact temperature that exists in the viscometers.

United States Patent 1191 HllS 1 July 10, 1973 METHOD AND A DEVICE FOR[56] References Cited 7 DETERMINING THE TEMPERATURE AT UNITED STATESPATENTS VISCOSITY MEASUREMENTS 3,302,451 2/1967 Martin 73/55 [75]Inventor: Gilles Gerardus Hirs, Pijnacker, 3,314,294 4/1967 Como"Netherlands 3,533,290 10/1970 Babcock et al. 73/357- AssigneelNedel'lands organisatie v00! Primary Examiner-Richard C. QueisserToegepast Namul'wetenxhappelllk Assistant Examiner-Frederick ShoonOnderzoek Ten B hoer V n Auome Hammond & Littell Nijverheid, Handel enVerkeer, Hague, Netherlands [5 7] ABSTRACT [22] Fil d; D 10, 1970 Twocapillary-viscometers which are identical except for differing asregards the extent to which the width of [21] App! their capillariesdepends on the temperature, are simultaneously used for identicalmeasurements under iden- [30] Foreign Application Priorit D t ticalconditions. The ratio of the two measuring values Dec 12 1969Netherlands 6918731 is a direct indication for the exact temperaturethat exists in the viscometers- [52] U.S. Cl 73/344, 73/54, 73/357 6Claims, 3 Drawing Figures [51] Int. Cl.. G0lk 11/00, GOlk 13/02, GOlnll/04 [58] Field of Search 73/344, 357, 55, 73/54 RATE RATIO fi SENSOR lI I 13 s 13 Patented July 10, 1973 RATE SENSOR INVENTOR.

GILLES GERARDUS HIRS BY ATTORNEYS METHOD AND A DEVICE FOR DETERMININGTHE TEMPERATURE AT VISCOSITY MEASUREMENTS The invention relates to amethod for determining the temperature at viscosity measurements ofliquids with the aid of viscometers of the type in which the liquid isfed through a capillary under the influence of a known difference inpressure and the rate of flow or a magnitude immediately related to itis measured.

It is known in the viscosity measurements art to place the viscometer inan environment that is kept at a controllable temperature, and to carryout the measurement when it may be assumed that the viscometer hasadopted the ambient temperature.

This assumption constitutes an uncertain factor and may lead to errorsthat are unpermissable for accurate measurements.

Therefore it is of importance at viscosity measurements to know theexact temperature in the viscometer, because this opens up thepossibility, to adjust and keep the temperature accurately at a desiredvalue.

It is the object of the invention to provide for these temperaturemeasurements a method that does not require special equipment but can becarried out with the viscometers themselves and simultaneously with theviscosity measurements.

To this end the method according to the invention is characterized inthat two identical measurements are carried out with two viscometersthat mutually differ as regards the extent to which the passage of theircapillary is temperature-dependent and for the rest are identical toeach other, and then the ratio of the two measuring results isdetermined as a measure for the temperature pertinent to the viscositymeasurement.

For calculations have shown and experiments have borne it out that theratio of the measuring results of two viscosity determinations that,besides a difference in passage between the capillaries used, arecarried out under identical circumstances, depends exclusively on theabove difference in passage and this dependency is linear, provided thedifference is small in relation to the passage itself.

The direct result of this is that if the difference in passage is causedby a difference in temperaturedependence of the capillaries, there isalso a linear relation between the ratio of the measuring results andthe temperature in the viscometers.

This linear dependence holds good for viscometers in which a certainamount of liquid from a certain height flows through the capillary owingto its weight and in which the time required for it is determined, aswell as for viscometers in which the slit between a stator and aturbine-like rotor serves as capillary and the rotation speed of therotor is measured on feeding the liquid under a certain pressure.

As the above shows, with the aid of the method according to theinvention an exact temperature determination in the viscometers, by theviscosity measurements themselves and without the necessity of accurateequipment for temperature measurements is possible.

The invention also relates to a device for the execution of the methoddescribed. This device is characterized by two capillary-viscometerswhose two capillaries are shaped identical as a slit between an externalbody and an internal body at least partially embraced by the former andin which device by application of different materials the difference inthermal coefficients of expansion between the two bodies that togetherform a capillary, in the one viscometer is different from that in theother.

By making in such a device the two bodies, which together form acapillary, in the one viscometer of the same material and in the otherviscometer of materials with a difference in coefficients of expansion,in the first viscometer the capillary is not temperaturesensitive and inthe second it is, though, causing the desired effect to arise. In thisinstance the measuring result of the first viscometer determines theviscosity of the liquid and the ratio of the two measuring results theactual temperature at which the viscosity measurement was carried out.

If for the two bodies that form the capillary in the one visco-meter,two different materials are chosen and the same materials are applied inthe other viscometer but reversed, the temperature-sensitivity is twicethat of the above example. Then the viscosity of the liquid follows fromthe mean value of the two measuring results.

Starting from the well-established construction of capillary viscometersthe temperature-sensitivity of the device according to the invention canalready amount to some percents. per centigrade. The sensitivity can beconsiderably raised, however, by applying special appropriateconstructions.

For reliable measurements it is of importance that, mutually, theviscometers do not show any appreciable differences in temperature.

Therefore for both, the conditions should be the same as nearly aspossible, which for instance is attained by placing them together in asmall room, which is kept at a constant temperature and screened fromradiant heat.

A still better safeguard against undesirable differences in temperatureis obtained by uniting the two viscometers such according to a furthercharacteristic of the invention that at least one of the bodies thatform the capillary in the one viscometer has substantial thermal contactwith one, preferably the corresponding one, of the bodies that form thecapillary in the other viscometer. If for two corresponding bodies inthe two viscometers the same material is chosen and this material has agood heat conductivity, anoptimum safeguarding against differences intemperature is realized if these two bodies are in one piece.

It is possible to join more than two viscometers in the way as describedif special circumstances or requirements pertain, for instance forneutralizing interfering thermal or other influences.

The materials that are used for the bodies that form the capillaries maybe of several types. In general metals are the most suitable because oftheir heat conductivity and their processability into smooth surfaces.Preferably various types of rustproof metal are applied so as to preventchanges in the width of the capillary caused by deposits on the surfacewhich could also effect the surface. Other materials, however, such asplastics and ceramic materials, provided with a coating of a differentmaterial, if necessary, may also be applied to meet particular demandsin view of, for instance, chemical activity of the liquid or extremetemperatures.

The invention is further elucidated below with reference to the drawing.In it FIG. 1 shows a part of a device according to the invention incross-section;

FIG. 2 shows an upper view of it;

FIG. 3 in cross-section shows a device according to the inventioncomposed of a different type of viscometers.

The device of which FIGS. 1 and 2 show a part comprises two bodies 1 and1', which with a flat side are attached or clamped to each other. Eachof these bodies 1 and 1 has a bore, respectively 2 and, in which at oneside is mounted a core, respectively 3, and in a way that is notspecified.

Because cores 3 and 3' have a diameter, which is slightly smaller thanthat of bores 2 and 2' there is a slit, respectively 4 and between cores3 respectively and 3 and bores 2 and 2 respectively. These slits 4 and 4are the measuring capillaries of two viscometers, which for that purposein the usual way are provided with means, not shown in the drawing, soas to feed a liquid at a certain pressure and means for determining flowparameters.

The width of slits 4 and 4 is chosen in dependence on the circumstances,such as the nature of the liquids for which the device is intended andmay, for instance, amount to to 100 t. In the drawing the width of slits4 and 4 is shown strongly enlarged.

In the event of changes in temperature of the two viscometers thediameter of bores 2 and 2' and that of cores 3 and 3 change. If body 1and core 3 are of a material with the same thermal coefficient ofexpansion, these changes in diameter do not affect the width of slit 4.In the event of a difference in coefficient of expansion the width ofthe slit changes in proportion to the changes in temperature and thedifference in coefficient of expansion and a different measuring resultis obtained.

If between body 1' and core 3 there is the same difference incoefficient of expansion, the measuring result that is obtained withslit 4? changes to the same extent as in the event of slit 4. If herethe difference in coefficient of expansion is different, however, thechange in the width of slit 4' is not the same as that of slit 4 and twodifferent measuring results are obtained, too.

When with two capillaries with somewhat unequal widths but for otherwiseidentical conditions the same measurement is carried out, two differentmeasuring results are obtained, whose quotient is independent of therest of the variable magnitudes, such as the viscosity of the liquid andthe pressure with which this is fed through the capillaries. As thedifference in slit width in the device described is the result of thedifference in temperature-dependence between slits 4 and- 4', the abovemeans that the quotient of the two measuring results is a directindication for the extent to which the existing temperature differs fromthe temperature at which slits 4 and 4' have the same width.

So as to realize the desired difference in temperaturesensitivity ofslits 4 and 4', for instance, bodies 1 and l and core 3 may be of thesame material and core 3' of a material with a different coefficient ofexpansion. Then there is the advantage that slit 4 is insensitive tochanges in temperature, so that the measuring result obtained with itdetermines the viscosity sought.

A greater sensitivity is obtained by making body 1 and core 3 of the onematerial and body 1 and core 3 of the other material so that at a changein temperature the width of the one slit increases as much as the widthof the other slit decreases.

In the device of which FIG. 3 shows a cross-section, two viscometers areapplied of a type with a freely rotating rotor.

In body 5 two bores 6 and 6' are provided in which rotors 7 and 7' fitwith a slight clearance. Rotors 7 and 7' have helical grooves 8respectively 8 and a deeper groove 9 respectively 9. Bores 6 and 6' areprovided with corresponding circular grooves 10 respectively 10', whichboth communicate with liquid feeding duct 1 1 over and under rotors 7and 7' bores 6 and 6' have open liquid discharges l2 and 12'respectively 13 and 13'.

On feeding a liquid under pressure via duct 11 and grooves 10 and 10' tothe slit between each of rotors 7 and 7' and bores 6 and 6' in them apressure build-up arises that centers and supports rotors 7 and 7', sothat they have no direct contact with body 5.

Owing to the flow of liquid that occurs in the slits in the direction ofthe discharges and the presence of helical grooves 8 and 8 rotors 7 and7' begin to rotate. The speed with which they rotate depends on the rateof flow in the slits and so, at a given pressure, on the viscosity ofthe liquid.

If rotor 7 consists of the same material as body 5, the width betweenbore 6 and rotor 7 is not affected by changes in temperature. If, on thecontrary, rotor 7 is of a material with a greater coefficient ofexpansion than the material of body 5, then at a rise in temperature theslit between bore 6' and rotor 7 becomes smaller, causing the rate offlow of the liquid and the rate of rotation of rotor 7' immediatelyrelated to it to decrease.

This change in rate of rotation is only dependent on the change in slitwidth and so on the change in temperature. The result is that the ratioof the rates of rotation of rotors 7 and 7' sensed by rate ratio sensor14 gives a direct indication about the extent to which the temperaturein the viscometers differs from the temperature at which the twoviscometers have the same slit width.

I claim:

1. A device for determining the temperature at which viscositymeasurements of liquids are made comprising two capillary-viscometerswhose two capillaries are identically shaped and each formed as a slitbetween an external body and an internal body at least partiallyembraced by the external body, the two bodies that together form acapillary in the one viscometer having a thermal coefficient ofexpansion different from the two bodies forming the other capillary, andmeans to determine the ratio of said viscosity measurements to producesaid temperature determination.

2. A device according to claim 1, wherein at least one of the bodiesthat constitute the capillaries of the two viscometers partiallyconsists of a material whose thermal coefficient of expansion differsfrom the material of which the rest of the bodies consists.

3. A device according to claim 1, wherein the external and internalbodies that together form a capillary in one viscometer have differentthermal coefficients of expansion, and the external and internal bodiesthat together form the other capillary in the other viscometer each havea coefficient of expansion equal to that of the opposite respective bodyin said first capillary.

4. A device according to claim 1 wherein at least one of the bodies thatform the capillary in one viscometer through two capillaries under theinfluence of a known difference in pressure and simultaneously measuringthe flow rate or a value related to the flow rate, the two viscometersbeing identical except for different capillary temperature dependenceand determining the ratio between said measurements whereby the ratio ofthe measured flow rates measures the temperature pertinent to theviscosity measurement.

1. A device for determining the temperature at which viscositymeasurements of liquids are made comprising two capillaryviscometerswhose two capillaries are identically shaped and each formed as a slitbetween an external body and an internal body at least partiallyembraced by the external body, the two bodies that together form acapillary in the one viscometer having a thermal coefficient ofexpansion different from the two bodies forming the other capillary, andmeans to determine the ratio of said viscosity measurements to producesaid temperature determination.
 2. A device according to claim 1,wherein at least one of the bodies that constitute the capillaries ofthe two viscometers partially consists of a material whose thermalcoefficient of expansion differs from the material of which the rest ofthe bodies consists.
 3. A device according to claim 1, wherein theexternal and internal bodies that together form a capillary in oneviscometer have different thermal coefficients of expansion, and theexternal and internal bodies that together form the other capillary inthe other viscometer each have a coefficient of expansion equal to thatof the opposite respective body in said first capillary.
 4. A deviceaccording to claim 1 wherein at least one of the bodies that form thecapillary in one viscometer has a substantial thermal contact with oneof the bodies that form the capillary in the other viscometer.
 5. Adevice according to claim 4, wherein at least one of the bodies thatform the one capillary and the corresponding one of the bodies that formthe other capillary both consist of thermally conductive material.
 6. Amethod for determining the temperature at which viscosity measurementsof liquids are made with capillary viscometers which comprises feedingliquid through two capillaries under the influence of a known differencein pressure and simultaneously measuring the flow rate or a valuerelated to the flow rate, the two viscometers being identical except fordifferent capillary temperature dependence and determining the ratiobetween said measurements whereby the ratio of the measured flow ratesmeasures the temperature pertinent to the viscosity measurement.